Don't some people stream snipe in order to stream cheat? - Well tbh I don't really know, but i suspect most of the time it happens they just quickly load up the stream at the beginning of the game. Also, I think it is possible to hide exactly when you are searching for a match with overlays etc.
The only downside I can see is that the top of the ladder will look like a bit of a mess if half the people's names are IIIIIIIIIIIII, but I would hardly care about this from a players perspective. Blizzard have placed the issue of stream cheaters completely outside their control, so they cannot complain if players react in this way to deal with the issue.
I actually think that less stream cheating goes on than streamers believe, but this would if nothing else set their minds at ease.